Summary
We propose to adopt a new airworthiness directive (AD) for all General Electric Company (GE) GEnx-1B turbofan engine models. This proposed AD was prompted by reports of GEnx-1B engine oil loss. This proposed AD would require removal and replacement of the non-conforming ball valve in the oil filler cap. We are proposing this AD to prevent loss of engine oil, which could lead to failure of one or more engines, loss of thrust control, and damage to the airplane.